1. Field of the Invention
The present invention relates to a display apparatus and a control method thereof.
2. Description of the Related Art
In a recently proposed method for improving a light emission efficiency of a light source that emits light using a commercial alternating current power supply, alternating current/direct current conversion and direct current/voltage conversion are not performed, and instead, a plurality of LEDs connected in series are driven to emit light using an alternating-current voltage as is, thereby reducing loss occurring during the respective conversions. The alternating current-driven LEDs emit light in a period of the alternating-current voltage.
In a display apparatus including a backlight, a power consumption of the backlight occupies a large proportion of an overall power consumption of the display apparatus. Therefore, the overall power consumption of the display apparatus can be reduced by reducing the power consumption of the backlight. By subjecting a light source of the backlight to alternating current driving, the power consumption can be reduced greatly.
However, when the light source of the backlight is subjected to alternating current driving, a frame rate of a video signal and a light emission period of the backlight become asynchronous, and therefore, as shown in FIG. 8, the backlight may emit light during a transmittance transition period (a shaded portion of the drawing) of a liquid crystal panel. When the backlight emits light during this transition period, sharp video display is impaired. More specifically, a double image consisting of front and rear frames is displayed, and therefore motion blurring occurs during display of a moving image.
Meanwhile, an image pickup apparatus that detects flicker using a flicker detecting light source and controls an image pickup frame rate and a flicker index value detection period when flicker is detected has been proposed in the related art (see Japanese Patent Application Publication No. 2005-229353, for example).